Advent Children: Secrets of a Locked Heart
by Ava Chanel
Summary: "She is grateful that he does not suffer a similar fate of the puppet that she has become- while the General enjoys every moment of it." A retelling of Advent Children, with Tifa Lockhart being the one who contracts the disease of Geostigma instead of Cloud. Sephiroth x Tifa x Cloud
1. Black Butterfly

**A/N: **_Been a while since I've written anything for this fandom, but I'm back with a little something. :) Tifa is my favorite character from this series (as many of you know), and I always love writing stories centred around her. So, this is my take on Advent Children, with a twist._

"Underneath the skin there's a human  
Buried deep within there's a human  
And despite everything I'm still human  
But I think I'm dying here..."

-animal, daughter

* * *

**Advent Children: Secrets of a Locked Heart**

_Prologue: Black Butterfly_

* * *

She wanted to _sleep_.

It was her time, she'd lingered long enough, and she was so very tired. The ebb and flow tugged at her conscience, sang her a lullaby that freed her of all her aching memories. They became a part of one another, melded together. She could feel herself slipping, and it was calming to float there in the waves as they crashed softly against her.

She was ready to go.

Bu there was a disturbance, then.

She could feel it, slight though it was, like she always did. It was enough to jolt her, to fight off the sleep that plagued her. Her duty was to keep it in check, keep its insatiable hunger always at bay. She seeked for it, probed for it with her mind, fearing the worst. It got stronger as she moved along, pulsing to life with every oncoming wave; an indicator that she'd failed this time.

_Anger_.

_Hate_.

_Vengeance_.

So much of it, overwhelming her all at once until she was left drowning in it. No longer was the flow calm; it raged as if a storm was on the horizon, and she tried to fight it, to claw her way to the surface. She struggled against its evil current, and all of it came back to her in a single movement. No longer was there peace.

She was drowning in the thick, black liquid. Like a poison, it seeped and contaminated all around it. The first memory that came back to her, was always the same one. She knew then, she wasn't ready to leave just yet. Her work wasn't done. She couldn't leave _him_.

_Cloud._

Her memories echoed the name, rebuilt the image of glowing cerulean eyes, wheat coloured hair, upturned nose, ribbon shaped lips. She sent it into the ripples across the waves, and it was perhaps, her first mistake.

As soon as she recalled it, the waves around her grew more violent and angry. They twisted and contorted, confining her within them, like a whirlpool she could not escape. They joined her conscience in speaking the name, building the memory. Except, the voice was full of loathing and evil. It drowned her out, took control, and she was left powerless.

_Help!_

She needed help. She had to find a way out, had to stop the contamination. It told her it was too late. The poison had reached a substantial amount, and there wasn't an ounce of purity left. But she had to protect him, so she fought against it anyways; a battle she could never win.

The storm raged on, spinning her about, toying with her. She had just been ready to sleep...

It quieted her, wanted her to stay out of the way. No more meddling from the Ancient powers. She moved against it until she could move no longer. She floated, helplessly, lifeless. But she could still watch as it worked.

She saw the thin, black like fingers spawn through the luminescent green, stretching as far as they could go. All the while, they echoed the name, remembered their hatred for the one responsible. With her out of the way, it was only a matter of time...

It would find its path to him, no matter who it got to first. It would find him sooner or later. It had a plan, and casualties weren't something it cared for. It would eliminate all who stood before it.

There would be three pieces.

It flowed in three different directions, infecting all it could.

Three instruments, one vessel. It was not afraid to let her glean that much of its plot when it's conscience fused with her own.

To accomplish the impossible, that was what it required.

She was the observer now. By the time she would be able to break free, it would be too late...

It had already found its first mark. She agonized at the thought of the children. Malicious and cruel, it cared not for whom it bestowed its kiss of death.

Her last thought was the same as her first one...

_I'm sorry,_ _Cloud..._

* * *

It looked like a butterfly.

Small, black, in the centre of her back and along her spine, its wings stretching outward. It marred her once fair skin. Barely noticeable. But it was there, and that was how it had started.

It didn't hurt yet. Didn't even beckon an itch. Maybe it would go away, fade away into a scar, like the many that already decorated her skin.

She examined it in the bathroom mirror, indifferent. She rubbed it, touched it, watched how it was so perfectly imbedded into her body. It moved this way and that, stretched with her. Anyone could have assumed it was just a birthmark, or a beauty mark. But she knew better. The suspicious little symbol had only recently become a part of her.

She'd stayed optimistic. It hadn't grown much in size over the past few weeks. There was no need to alarm anyone. She'd kept it to herself this long, she may as well hold on a while longer. It was possible that it wasn't a symbol of the rampant, infectious and deadly disease. Or so she liked to tell herself. She'd experienced none of the similar symptoms, although she was aware that each and every case was unique to the individual. In a strange way, it was still beautiful. The thought was strange and foreign to her, but it was there.

She caught herself staring at it, entranced by the uneven lines and curves, and the way it blended with her. Where it ended, and _she_ started. For a fleeting second, she thought she saw it move, pulse against her like a parasite leeching her very life. She rubbed her eyes, and figured it was because she hadn't blinked. She was just seeing things.

It was best she told no one.

She convinced herself of it, even as she reluctantly put on her clothes. She would wear her smile, her cheerfulness despite the fact. She'd put on the show for her friends. It was bad enough that Barret worried about her incessantly. He was on Cloud's case for his frequent absence already. Were he to find out that she'd been infected, he'd blame his old comrade in a heartbeat. She didn't want them to fight. Things were hard enough as it was. And if Cloud were to find out, well...she didn't really know what to make of that.

Taking in a deep, shaky breath, she stepped out of the bathroom, and returned to her duties. The world wouldn't stop turning just because she was sick.

Still...

She couldn't quite shut the nagging voice in the back of her mind, telling her of her imminent doom, of the harsh reality, even as she worked the bar and poured the drinks...

Tifa Lockhart was dying.

* * *

**A/N:**_ To be honest, I'm not the biggest fan of AC. However, I did think it had a semi decent plot. There were certain aspects that didn't work well, in my opinion, so I'm obviously not going to be following through with it entirely. I'm making changes, adding twists, and basically creating something a bit more of my own. So no, this isn't really a novelization of the movie. We'll just see how it all goes. :) Feedback, as usual, is welcomed. _


	2. Mine

**A/N: **_Thank you to all who have reviewed and followed the story. Hopefully, I don't disappoint._

* * *

**Advent Children: Secrets of a Locked Heart**

_Chapter One: Mine_

* * *

She'd been pouring her drinks, as per usual, when it first happened. The pain had started gradually, barely anything more than an ache. But it grew in intensity, until it left her practically crippled. Her hand shook, her body swayed, her stomach flipped, and the room spun about her. Tifa Lockhart felt like she was going to pass out. Heat radiated off of her, blood rushing to her face as she waited for the moment to pass. It was only ever for a few seconds, but while she was enduring the experience, it felt more like hours. Her customers had noticed something was off, and Tifa was grateful that the geostigma had marked her somewhere that wasn't entirely visible. Otherwise, she'd have lost her entire clientele. It was bad enough that she had to keep Denzel hidden during business hours. There was so much negativity associated with those infected, that those who were still clean desperately segregated themselves from those who were dying.

The mark had gotten bigger now. As was expected, it would only continue to grow as time passed. The black butterfly was stretching out its wings, reaching out just a little bit further every time Tifa would chance a look at it in the mirror. Sometimes, she could swear it pulsed to life, the skin beneath it boiling up, as if something was trying to get out. In the next moment, it was stilled like a birthmark, and Tifa was left feeling like she had a very overactive imagination.

"Are you alright, Miss?"

Her eyes had glazed over, and as they regained focus, she was staring up into the face of a regular customer. He watched her with concern in his expression, and offered her a hand to help her stand up. Tifa grabbed it, got to her feet, and brushed herself off, trying her best to ignore the lingering stares and whispers from her customers.

"I'm fine, thank you...," she managed to choke out in a strained voice.

She cleared her throat, and offered up one of her most gracious smiles to keep things calm.

"I must be exhausted. I had to pull an all nighter recently. I guess I might have pushed myself a little too hard...," she explained.

In a couple of seconds, things went back to normal, and the bar was bustling with conversation again, as Tifa got back to work. She composed herself, because she had to. But she knew that, soon enough, she'd be no better off than Denzel; bedridden, sick, sleeping more than she should, and not eating enough. She had to say something soon, she knew that.

But Cloud had so much on his plate as it was, and she wasn't sure how he'd even handle such news...How would she even go about telling him? She didn't even want to think about it, so instead, she pushed it to the back of her mind, and moved along with her day.

When her last customer for the day had left, Marlene had hobbled down the stairs, looking worn out for a child her age. Her lids were heavy with sleep, her hair a greasy mess, and her skin paler than usual. Still, she came down to help Tifa tidy up the bar. The older woman smiled at the child and shook her head; "Don't worry about the dishes. I can manage. You go start running the bath; I'll be up in a minute."

Marlene rubbed at her eyes before nodding, and walked back the way she came, little feet practically dragging. "Okay..."

She'd spend the entire day at Denzel's side, monitoring his head wound, and keeping him company. Denzel had hated it, and that was why Tifa had tried relieving her of the duty every once in a while...it was also how she'd come to be infected, as well...

She remembered the day so vividly, but could never bring herself to blame the child. It hadn't been his fault, truly. She'd been a little too careless, not cautious when she should have been. Tifa had come out of the shower late one night, and caught Denzel passed out on the couch in front of the TV. With nothing but her towel on, she had hoisted him up on her back, and carried him up the stairs to his bed. He'd rested his head on her exposed spine, and that was exactly where the mark had first shown itself...

It would eat him alive to know that he'd been the cause. Even though she would never, ever blame him, she knew that Denzel would have it haunt him to his grave. In that regard, he was much like her childhood friend.

As per usual, Cloud hadn't come home that night, and Tifa had given up on waiting for him. As the late hours creaked on past, and the bar was cleaned and fully supplied for the next day, she found herself growing drowsy. Yawning, she stretched her arms over her head before taking a peek at the time. It was early in the morning, and she had to be up in a couple of hours. She went upstairs to her room, and collapsed into her bed, waiting for sleep to overtake her body.

That night was when the dreams had started.

Nightmares were a common occurrence for her, usually replaying her father's gruesome death, and her hometown burning to the ground. Sometimes, even, her mind was horrible enough to play out the scene of Aerith's sacrifice, over and over again. Praying, smiling, and then skewered by Masamune the next moment, blood tainting the pink dress, spilling to the floor, and running through the creases.

Drip...

Drip...

Drip...

And she was helpless, frozen, and unable to do a thing, besides watch in terror; watch another life slip away forever.

But those were of the typical ilk she was used to. The geostigma dreams were far worse, and she could barely make any sense of them, even as they were happening.

She wasn't a person in those dreams. She wasn't herself. She'd be floating through the stream, calm and warm as it enveloped her in its waves. It hushed her, sang an ancient song of slumber and peace. But there was so much anger, so much contempt. She wanted _vengeance_. She wanted _destruction_. She wanted to _kill_. It was so overwhelming that, eventually, it drowned everything else out, and the waves became violent, bending to her will. It excited her to know that at last, she was in control again.

And then, it shifted, and she was herself once more; an outsider, watching as it happened. Luminescent green eyes flashed to her, and it made her gasp for air, shocked and terrified by the way they watched her. She struggled to breathe for a moment, and those same, cat-like eyes glared at her.

Long, black wisps that resembled claws reached for her, stretching and aiming for her neck. They were suddenly around her; gripping, choking, and strangling her. She tried to fight, kick them off, but it was no use. It had her. This was it. This was how she was going to die.

_No...not die...Not yet..._

The voice was unnatural, unrecognizable, but familiar all at once. It did not have a gender or an entity; it was as if it came from her own head, from within _her_.

The mark on her back was burning, growing at an impossibly fast rate, until the wings engulfed her entire body, and pushed through her skin. The pain was blinding. She tried to cry out, but she was still unable to make a sound. The claws squeezed tighter around her throat, like nails digging into her flesh.

She woke up in a panicked sweat just as she was feeling her life leave her body in the nightmare. She gasped, noting the tangle of her sweat soaked sheets about her feet. She'd been tossing and turning, her heart hammering against her ribcage, as if it beckoned to make a hasty exit through her ribcage.

It was just a dream.

A weird dream, but a dream nonetheless. None of it was real. She reminded herself of this as she tried to steady her breathing.

She'd gotten up, and decided to get a cold drink of water, her mouth as dry and parched as the Corel desert at its hottest. A cool cup of water would help balance her nerves, make her less twitchy at every shadow, and suppress the goose bumps that decorated her fair skin. She welcomed the feeling of the cool tiling beneath her bare feet, and wiped at the sweat that had her bangs sticking to her face.

When she'd clambered down the stairs, and flicked on the lights, she noted a few things that indicated Cloud was home.

She saw the delivery boxes all set to go by the door, saw his sword leaning against the wall by his muddied shoes. His fresh, dirty dishes were in the sink, probably he'd have just eaten some breakfast. Tifa wondered how long she'd slept that she'd missed his appearance.

"Tifa? Why're you up at this hour?"

His voice jolted her out of her still somewhat sleepy state, and she turned to acknowledge the fair haired swordsman who lived with her. She felt like a mess, her clothes amok from her active nightmare, and her hair a gross mop of dark brown strands clumped together. Cloud didn't seem to be phased by any of it, though. Instead, his eyes wandered to her neck, and they widened like saucers. In that instance, he took a step towards her, closing the distance between them in a single stride. He raised his fingers to the tender spot, but hesitated in touching the skin.

He whispered, "What the heck is that...?"

"What?" Tifa had no idea what he was talking about. Self consciously, she touched her throat with her own fingers, only to jump at the slight ebb of pain from where they'd pressed into her skin. Cloud watched her with suspicion and concern, his brows furrowed in thought and his mouth parted as if to speak. Tifa jolted to the bathroom, feeling her heart rate escalate as she recalled the dream, fresh like a new cut. When she turned on the bathroom light, she saw it, then.

Bruises.

Purple and ugly and marring her delicate flesh...

What was even more unnerving about them was that they were in the shape of unnaturally long fingers, stretching around her neck horizontally...like a chokehold.

She recalled the black wisp-like claws, squeezing her throat so tight, constricting.

Cloud was at the bathroom door then, worry obvious in his glowing, cerulean eyes.

"Did you wanna talk about it?" He asked her, as she left the bathroom and sighed into her hands.

Tifa shook her head, "I...I don't know how it happened...Maybe it's an allergic reaction?"

She couldn't help the lie that slipped from her mouth. She watched Cloud watching her, and prayed that he didn't see through her. He appeared stern and serious in that moment, his arms crossed over his chest as he examined her.

With a sigh, he made his way towards the things he'd need for his next delivery run. "You should have it checked out...," he told her as he strapped the abnormally large sword onto his back.

"I mean it, Tifa...That looks...serious," he added, looking at her with one of his softer expressions.

She mustered up a smile, and hugged her bare arms, nodding in agreement. "I'll visit the clinic when I get the chance."

But life moved forward, and Tifa had a schedule to keep. She wore a scarf around her neck at work, despite the strange stares and questions she got all day. She didn't know how else to cover it up. It was starting to terrify her...She'd had nightmares many times over, woken up from them with a start almost every other night when the wounds were still new. But never had they felt so...real. She was scared of going back to sleep, scared of what was going to visit her this time in her dreams. She'd scoured for information on night terrors and geostigma, and found no connections. It quickly became apparent that whatever route her sickness was taking, it wasn't the typical one assigned to most of those infected.

Whenever she was alone, she was acutely aware of the silence, aware of every shadow, and every small sound. It gave her a headache, made her break out into a cold sweat, made her feel as if time was slowing down and that there was evil about. She felt like a lost child, desperate to find the company of another human if only to appease her mind and her anxiety. But perhaps the worst was when she'd sometimes hear that familiar voice, the same one that seemed to originate within the deepest part of her mind from her nightmares...

It laughed at her, and when it addressed her, it simply called her...

_Mine..._

* * *

**A/N: **_I understand that it's short and slow, but I feel like I need to establish some ground here, cement out a few differences from AC and this piece of work. It also allows me to ramp up the horror aspect to this story because, in a way, it starts off a bit like one. Feedback is appreciated. :)_


End file.
